| 摘要 |
PURPOSE:To provide a digitizer which has high speed and high accuracy, is small in power consumption, is not affected by radiation, does not becomes a radiation source and is comparatively inexpensive in manufacturing cost. CONSTITUTION:This digitizer uses the sound wave transmitting from a stylus 50 for determining the location of the stylus 50 on a plate. The sound wave is introduced from the chip of the stylus 50 to the plate and is detected by plural detectors D1 to Dn arranged along the surrounding of the plate. By sensing the difference of the reaching time of sound wave in each detector D1 to Dn, the location of the stylus 50 is calculated. In a suitable embodiment, four detectors are arranged at each corner of a rectangle and the difference of time is used as the address within a look-up table. The look-up table stores the x and y coordinates corresponding to the difference of time. In other embodiments, the location of the stylus is determined by detecting the only 'fast' symmetrical wave or the 'slow' antisymmetrical wave generated within the plate or using the reaching time of the both waves.
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